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    Femoral head and large joints

    Background

    Larger specimens of bone include femoral head, humeral head, femoral condyles and tibial plateau removed during joint replacement surgery.1 Removal of these is usually performed for degenerative joint disease (osteoarthritis), avascular necrosis, fracture and sometimes for inflammatory arthritis.

    See separate protocol for bone tumour and soft tissue tumour specimens.


    Record the patient identifying information and any clinical information supplied together with the specimen description as designated on the container. See overview page for more detail on identification principles.

    • No
      • Non-routine fixation (not formalin), describe.
    • Yes
      • Special studies required, describe.
      • Ensure samples are taken prior to fixation.
    • Not performed
    • Performed, describe type and result
      • Frozen section
      • Imprints
      • Other, describe

    See general information for more detail on specimen handling procedures.

    Inspect the specimen and dictate a macroscopic description.


    External Inspection

    Orientate and identify the anatomical features of the specimen.

    Specimen orientation

    Record additional orientation or designation provided by operating clinician:

    Record additional orientation or designation provided by operating clinician:

    • Absent
    • Present
      • Method of orientation (e.g. suture, incision)
      • Feature denoted

    Describe the following features of the specimen:

    Procedure

    Record as stated by the clinician.

    • Total joint arthroplasty; hip, knee or shoulder
    • Revision of total joint arthroplasty; hip, knee or shoulder
    • Other, describe

    Anatomical components included (more than one may apply) and specimen dimensions (mm)

    Describe the components present and measure as applicable.

    • Total specimen, in three dimensions
    • Femoral/humeral head
    • Femoral neck
    • Femoral condyles
    • Tibial plateau
    • Other, describe

    Specimen integrity

    • Intact
    • Disrupted/fragmented, describe

    In any setting where crystal deposition disease is suspected, formalin fixation, subsequent decalcification and haematoxylin staining are likely to dissolve crystalline structures. In such cases, a scrape smear (prior to processing) of any chalky substance examined under polarised light is optimal.

    Larger specimens should be examined from all angles as changes may be focal.

    Photograph the specimen to record all salient features:

    • Femoral/humeral head
    • Femoral neck
    • Femoral condyles
    • Tibial plateau

    Note that these features require macroscopic assessment of the specimen while intact and after dissection.

    Description

    • Shape of the weight-bearing surface
      • Flattened (as in osteoarthritis)
      • Saddle-shaped (as in late stage avascular necrosis or subchondral fracture)

    Articular cartilage

    Describe any abnormalities present.

    • Defects
      • Absent
      • Present, specify location and size (mm)
    • Linear folds
      • Absent
      • Present, specify location and size (mm)
    • Eburnation
      • Absent
      • Present, specify location and size (mm)
    • Step depressions
      • Absent
      • Present, specify location and size (mm)
    • Other, specify

    Osteophytes

    Describe and measure all osteophytes:

    • Surface or peripheral (specify)
    • Size in maximum dimension (mm)

    Synovium

    Describe any abnormalities present.

    • Pannus extending from the perimeter and along the surface (as in inflammatory arthritis)
      • Absent
      • Present
    • Chalky white material on surface
      • Absent
      • Present

    Any chalky material (possible crystalline material) should be smeared on to a slide and examined with polarisation microscopy prior to processing.


    Dissection

    Large specimens containing bone are slow to fix and require initial dissection prior to fixation and decalcification.1-5 See separate decalcification protocol for more information.

    Various saws are available for the dissection of bone; hand saws, band saws and/or diamond-coated saws. Selection of appropriate equipment will depend on the resources in a particular laboratory.1-5

    In general, these larger bone specimens should be sectioned in the coronal plane to correspond with an anterior-posterior radiograph. As changes may be focal, serial sectioning is recommended in all cases. Optimally the specimen should be sectioned at 5-6mm intervals, creating between six and eight slabs.

    Gently brush and wash each surface thoroughly to remove bone dust. Only relevant slabs should be transferred for decalcification (in an appropriate solution). The entire structure should never be placed in decalcification solution.

    The bone is orientated in such a way that fragile or detached cartilage is pressed against a firm surface minimising distortion and loss of any necrotic bone or cartilage. The specimen is sectioned with the articular surface down and sawing towards the articular surface starting with relatively firm areas and gradually reaching the fragile subchondral wedge shaped area of osteonecrosis and the area of possible cartilage detachment.2

    Allow to fix sufficiently, brush and wash thoroughly before transferring for decalcification in appropriate solution.

    After sectioning the specimen may require longer fixation in larger quantity of formalin.

    Photograph the dissected specimen, if required.

    Note photographs taken, diagrams recorded and markings used for identification.


    Internal Inspection

    Describe the cut surface appearance including the following items:

    • State of the articular surface
    • State of the subchondral dome
    • Presence of discolouration of bone or cartilage
    • Presence of softening, sclerosis, cysts, fibrous or fibrocartilaginous areas or fracture

    In larger arthroplasty specimens in a setting of fracture, the presence or absence of a screw track or other internal fixation device should be described and the nature of the lining of the screw track elucidated. In some it merely represents part of the surgical process where there would be no reaction but in some the screw may have been present for some time; in which case reactive changes would be noted in the surrounding tissues.


    Processing

    Submit representative sections of the lesion demonstrating relationship with adjacent tissue.

    • Slabs should be dissected and sectioned in order to best display the relationship of the articular cartilage with the subchondral bone.
    • In femoral heads and humeral heads this is best achieved in a fan-like manner, the apex of the fan being in the subcapital region. This also allows reconstitution for overall review of the distribution of the changes.
    • Sections of femoral condyles and tibial plateau are best taken in the anterior-posterior coronal plane and any distinction between changes on medial and lateral compartments noted.
    • Articular surface with underlying bone, normal and abnormal, 1-2 slabs
    • Synovial tissue if present, 1 section
    • Areas of probable necrosis including interface with adjacent, macroscopically-normal bone, 1-2 slabs
    • Soft tissue, 1 section
    • Submit representative tissue, 1-2 slabs ensuring adequate assessment of the fracture site
    • Soft tissue, 1 section

    Subchondral fracture may mimic avascular necrosis (AVN) clinically and in radiographs due to collapse of the articular surface. Distinction is based on recognition that the zone of abnormality is confined to the subchondral plate and lacks the characteristic deep and wedge shape of necrosis seen in AVN.

    Record details of each cassette.

    An illustrated block key similar to those provided may be useful.

    Block allocation key

    Cassette id
    Site
    No. of pieces
    A-B
    Articular surface
     
    C
    Synovial tissue if present
     
    Cassette id
    Site
    No. of pieces
    A-B
    Areas of probable necrosis with adjacent, macroscopically-normal bone
     
    C
    Soft tissue
     
    Cassette id
    Site
    No. of pieces
    A-B
    Fracture site
     
    C
    Soft tissue
     

     

    Acknowledgements

    Associate Professor Fiona Bonar for her contribution in reviewing and editing this protocol.


    References

    1. Freemont AJ, Denton J and Mangham DC. Tissue pathways for bone and soft tissue pathology, The Royal College of Pathologists, London, 2011.
    2. Dimenstein IB. Bone grossing techniques: helpful hints and procedures. Ann Diagn Pathol 2008;12(3):191-198.
    3. Bancroft JD and Gamble M. Theory and practice of histological techniques. Churchill Livingstone Elsevier, Philadelphia, 2001;PA:744.
    4. Suvarna KS, Layton C and Bancroft JD. Bancroft's Theory and Practice of Histological Techniques. Suvarna KS, Layton C and Bancroft JD. Churchill Livingstone, 2013.

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      Femoral head 1

      Femoral head intact

      Femoral head 3

      Femoral head serially sectioned in the coronal plane

      Femoral head 4

      Femoral head sampled in a fan shaped manner from the subchondral region

      Femoral head 5

      Femoral head, representative blocks for processing

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      27-Mar-2019
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